1. Technical Field
This invention relates to the technology of hydraulically absorbing or dissipating shook energy and, more particularly, to shock absorber assemblies that use spring biased valves to change the energy absorbing characteristics while quieting or eliminating mechanical noise.
2. Discussion of the Prior Art
As shown in FIG. 1, automotive shock absorbers typically have a piston rod 10 supported on a chassis or autobody component 11 and also have a cylinder 12 supported on a wheel 13 through a knuckle 14 so that hydraulic attenuation (fluid flow from a compression chamber to an expansion chamber) may be established by oil confined in the cylinder in response to sliding movement of the piston within the cylinder. The amount of energy absorbed or dissipated is determined by the velocity of the piston rod that is retarder by fluid flow between the chambers and the cylinder.
Often supplementary or secondary valves are deployed to vary the amount and sequence of fluid exchanged between such chambers to give real damping characteristics to the absorbing effect or ride quality for the automotive vehicle. These secondary valves are biased to a closed position by a relatively light spring to give a precise low energy lift-off response, but such spring biased valves may suffer from chatter or wobble as the fluid flow exiting from the valve orifice creates vortices in the expansion chamber thereby destabilizing movement of the valve.
Attempts to overcome such chatter or noise have been limited; one such attempt uses elastic elements in the valve guide (see U.S. Pat. No. 4,331,224) but this use destroys parameters chosen to provide a very specific ride quality; there is little latitude in varying the shock absorber parameters (such as spring stiffness, spring preload, valve mass) if such ride quality is to be achieved.